Electrical Engineering · Question Bank

Synchronous Motors

81 of 112 questions match · page 4 of 5. Answer in your head first, then check the solution.

📘 EE Mock Board Exam

#61📘 EE Pocket Reviewer RojasEasy

Which of the following is used to start a small 1 synchronous motors?

ADamper windings

BVariable-frequency source

CDummy windings

DHand cranked system

#62📘 EE Pocket Reviewer RojasEasy

When a synchronous motor is operated without a load, how much is the approximate torque angle?

A45° electrical

B120° electrical

C0° electrical

D90° electrical

#63📘 EE Pocket Reviewer RojasEasy

Which of the following is a probable cause why a synchronous motor that has already started fails to develop full torque?

ALow excitation voltage

BReverse field coils

COpen or short circuited armature windings

DAny of these

#64📘 EE Pocket Reviewer RojasEasy

For the same active power drawn, what is the apparent power drawn by a synchronous motor in comparison to an induction motor?

AIt has more apparent power drawn

BIt has lesser apparent power drawn

CThey have approximately equal apparent power drawn

DAny of these

#65📘 EE Pocket Reviewer RojasEasy

Which of the following is true about a synchronous motor?

AIts speed is constant

BIts speed will drop slightly at full load

CIts speed is high at low torque

DIts speed is low at high torque

#66📘 EE Pocket Reviewer RojasEasy

A synchronous motor is said to be “floating” 1 when it operates under which of the following conditions?

AOn no load and without losses

BOn constantly varying load

COn a pulsating load

DOn a very high load

#67📘 EE Pocket Reviewer RojasEasy

What is the effect of increasing the load of a synchronous motor running with normal excitation?

AArmature current will increase but pf will decrease

BBoth armature current and pf will increase

CArmature current will decrease but pf will increase

DBoth armature current and pf will decrease

#68📘 EE Pocket Reviewer RojasEasy

Which of the following losses is not dissipated by the stator core surface in a synchronous motor?

ACopper losses in the slot portion of the conductors

BEddy current loss in the conductors

CIron losses in the stator

DWindage loss

#69📘 EE Pocket Reviewer RojasEasy

In a synchronous motor, the magnitude of the back emf set up in the stator depends on which of the following?

ARotor excitation

BRotor speed

CSupply voltage

DLoad on the motor

#70📘 EE Pocket Reviewer RojasEasy

What do you call the maximum value of torque that a synchronous motor can develop without losing its synchronism?

APull out torque

BSynchronizing torque

CBreaking torque

DStarting torque

#71📘 EE Pocket Reviewer RojasEasy

For the same active power drawn, what is the stator current drawn by a synchronous motor in comparison to an induction motor?

AIt has lesser current drawn

BIt has more current drawn

CThey have approximately equal currents drawn

DAny of these

#72📘 EE Pocket Reviewer RojasEasy

What is the value of the maximum torque angle in a synchronous motor?

A45°

B90°

C120°

D180°

#73📘 EE Pocket Reviewer RojasEasy

A synchronous motor running in normal excitation adjusts to load increases by how?

ABy increasing its power factor

BBy increasing its torque angle

CBy increasing its back emf

DBy increasing its armature current

#74📘 EE Pocket Reviewer RojasEasy

What type of rotor is used in a synchronous motor?

ASalient-pole type

BNon salient-pole type

CIts rotor is similar to a dc shunt motor

DIts rotor is similar to a dc series motor

#75📘 EE Pocket Reviewer RojasEasy

What is the full load slip of a synchronous motor?

AAbout 1% to 5%

BAbout 5% to 10%

CAbout 90% to 100%

DZero

#76📘 EE Pocket Reviewer RojasEasy

An under-excited synchronous motor is behaving like which of the following circuit elements?

AResistor

BCapacitor

CDiode

DInductor

#77📘 EE Pocket Reviewer RojasEasy

What is the purpose of embedding the damper windings in the pole face of a synchronous motor?

ATo eliminate hunting and provide enough starting torque

BTo reduce the windage loss

CTo reduce the eddy current loss

DTo provide more heat dissipation

#78📘 EE Pocket Reviewer RojasEasy

The rotor of a synchronous motor can only run at synchronous speed in which of the following reason?

ADue to Lenz’s law

BDue to Faraday’s electromagnetic induction

CDue to magnetization of the rotor poles by the stator magnetic field

DDue to the interlocking action between stator and rotor poles

#79📘 EE Pocket Reviewer RojasEasy

For the same active power drawn, what is the losses in the stator windings of a synchronous motor in comparison to an induction motor?

AIt has less losses

BIt has more losses

CThey have approximately equal losses

DAny of these

#80📘 EE Pocket Reviewer RojasEasy

Which of the following AC motors is usually used in large motor-generator sets?

ASynchronous motors

BSquirrel cage induction motors

CSlip ring induction motors

DRepulsion motors

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